Permanent magnets are often used as latches to mechanically couple components in devices. For example, permanent magnets can be included in a portable electronic device, such as a laptop computer (which is sometimes referred to as a ‘laptop’), to latch a lid to a base. In particular, permanent magnets may be included in the lid and the base. When the lid is proximate to the base, the permanent magnets may provide an attractive force that latches the lid to the base without consuming any power.
However, as the form factor in laptops is decreased, there may be less room for the permanent magnets. Consequently, the area and/or the thickness of the permanent magnets may need to be decreased. This may reduce the attractive force between the permanent magnets and the electromagnet, which may make the permanent magnets and the electromagnets less effective as a latch.
One approach for addressing this challenge is to increase the remnant magnetization of the permanent magnets. However, a larger remnant magnetization may increase the risk that the permanent magnets inadvertently damage components or devices that are sensitive to strong magnetic fields, such as credit cards. Because it is typically difficult to reduce or turn off the magnetic field provided by permanent magnets, the use of permanent magnets as latches in laptops may be less desirable.
In principle, electromagnets can be used to selectively provide magnetic fields and, thus, to latch the lid to the base. However, in practice, electromagnets consume considerable power and generate heat, neither of which is desirable in portable electronic devices such as laptops.